This application relates to an electrical generation system for use in an aircraft environment wherein a pair of generators is associated with a gas turbine engine, with one generator being constant frequency, and the other being a variable frequency generator.
Aircraft are typically provided with gas turbine engines, which include turbine rotors that rotate to provide power. Generators are associated with these gas turbine engines, and generate electricity from the rotation of a shaft driven by the turbine rotors. The electricity is utilized for various functions on the aircraft, including providing electric power to systems associated with the gas turbine engines, as well as providing electricity to other uses on the aircraft.
A gas turbine engine can rotate at varying speed. A simple generator driven by such an engine will generate a variable frequency.
It is known to provide a gas turbine engine with a pair of generators. In some cases, the generators have been variable frequency.
It is also known to provide a pair of constant frequency generators on a gas turbine engine. A constant frequency generator adapts to the engine's speed variation such that the generator still provides a constant speed and thus constant frequency output.
More recently, for several reasons, aircraft designers have wanted to utilize variable frequency generators. The use of the variable frequency generators raises some challenges, such as large, sustained, torsional oscillating loads in associated gear boxes, and a resultant increase in size and weight. Further, there is a limited no break power transfer (NBPT) capability. Also, many components associated with an aircraft require constant frequency power. Thus, complex motor controls have needed to be associated with each of these components to take the variable frequency electric power provided, and transform that into constant frequency power.